Trophic Aspects of Sperm Whales (Physeter macrocephalus) in the Northern Gulf of Mexico Using Stable Isotopoes of Carbon and Nitrogen

摘要

In the northern Gulf of Mexico (GoM), seismic operations and oil exploration are increasing in deepwater areas which are inhabited by sperm whales (Physeter macrocephalus). Yet, little is known about the feeding ecology of sperm whales. This report provides initial information on the variability in the relative trophic position of sperm whales in the northern GoM. Stable isotope ratios of carbon (C) and nitrogen (N) were measured from skin samples of free-ranging whales. The isotopic signatures were different between females and immature males. However, no differences were detected between samples from the Mississippi Canyon and samples from the northwestern GoM, perhaps due to similar consumption of average diet. We compared the isotopic values between individuals from the GoM and Gulf of California (GC), and between squid from inshore and offshore areas of northern GoM. The isotopic signatures of sperm whales from the GoM were contrastingly lower than whales from the GC. This isotopic difference may be associated with a variation in diet and different trophic level.